1. Technical Field
The technology described herein relates generally to wireless networking. More particularly, the technology relates to reducing a Peak-to-Average Power Ratio (PAPR) in a transmission using Orthogonal Frequency Division Multiplexing (OFDM) in a wireless network.
2. Description of the Related Art
Wireless LAN (WLAN) devices are currently being deployed in diverse environments. Some of these environments have large numbers of access points (APs) and non-AP stations in geographically limited areas. In addition, WLAN devices are increasingly required to support a variety of applications such as video, cloud access, and offloading. In particular, video traffic is expected to be the dominant type of traffic in many high efficiency WLAN deployments. With the real-time requirements of some of these applications, WLAN users demand improved performance in delivering their applications, including improved power consumption for battery-operated devices.
A WLAN is being standardized by the IEEE (Institute of Electrical and Electronics Engineers) Part 11 under the name of “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications.” A series of standards have been adopted as the WLAN evolved, including IEEE Std 802.11™-2012 (March 2012) (IEEE 802.11n). The IEEE Std 802.11 was subsequently amended by IEEE Std 802.11ae™-2012, IEEE Std 802.11aa™-2012, IEEE Std 802.11ad™-2012, and IEEE Std 802.11ac™-2013 (IEEE 802.11ac).
In a WLAN, minimizing a Peak to Average Power Ratio (PAPR) improves a throughput of communications in the WLAN while adhering to regulatory and device power limitations. A high PAPR is one of the most detrimental aspects in an OFDM system as it decreases the signal-to-quantization noise ratio (SQNR) of the analog-digital convertor (ADC) and digital-analog convertor (DAC) used therein while degrading the efficiency of the power amplifier in the transmitter. A PAPR of an OFDM symbol may be as high as 17 decibels (dB).
Recently, an amendment focused on providing a High Efficiency (HE) WLAN in high-density scenarios is being developed by the IEEE 802.11ax task group. The 802.11ax amendment focuses on improving metrics that reflect user experience, such as average per station throughput, the 5th percentile of per station throughput of a group of stations, and area throughput. Improvements may be made to support environments such as wireless corporate offices, outdoor hotspots, dense residential apartments, and stadiums.
HE transmissions in an HE WLAN include a preamble section different from that of previous WLANs. The preamble section may have one of the highest PAPRs of any portion of the HE transmission, especially when the preamble is duplicated across bandwidths of the HE transmission.